Thermal printer

ABSTRACT

The present invention is equipped with a plurality of print buffers for inputting print data into a thermal head, wherein such print data are selectively fed to simply change the current on-time for energizing the heating elements of the thermal head relative to specific information out of the entire information to be printed, thereby partially altering the color-forming degree on the recording paper to definitely distinguish the emphatic label portion from any other portion, and the current on-time for energizing the heating elements is shortened for any print line having none of the particular-color print data, hence reducing the required print time.

FIELD OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a thermal printer designed for printingscaled weight data and other contents on a recording paper by means of athermal head.

In general, employment of a thermal head as a printing means in a labelprinter or the like brings about a variety of advantages includingcapabilities for forming any desired print pattern and realizing clearprinting of a bar code. However, since the print color on the label asrecording paper is merely a prescribed one alone over the entiretythereof, when it is required to render some specific portion of theprinted information conspicuous for the purpose of emphasis, suchportion is customarily enclosed with a line or is printed in a thickerstyle. Although the above purpose is achievable to a certain degree bysuch conventional means, its effect is within the extent that sufficientcare is needed for recognition of the emphasis, and the emphasizedportion is not remarkably distinguishable at a glance.

The purpose mentioned can be accomplished with facility by multicolorprinting, which however requires two or more thermal heads toconsequently complicate the structure of the printing mechanism.

There is known a conventional apparatus which uses a single thermal headand a label having dichromatic color-forming temperature characteristicthereto, wherein the current on-time to energize the heating elements ofthe thermal head is so controlled as to print a desired label portion inred for optically emphasizing it.

According to such system, however, control of the current on-time isexecuted throughout the printing operation regardless of whether thelabel portion to be emphasized is merely fractional in most cases, sothat the time required for printing each line is prolonged to eventuallylower the efficiency with reduction of the label issuing speed.

OBJECT AND SUMMARY OF THE INVENTION

It is a first object of the present invention to display any desiredlabel portion, which needs to be emphasized out of the entire printinformation, in a particular color different from an ordinary one.

And a second object of the invention resides in preventing reduction ofthe paper issuing speed in the apparatus where the first object isachieved.

The present invention is equipped with recording papers each havingmulti-color-forming temperature characteristic, a thermal headcontaining a multiplicity of heating element and capable of printing therecording paper over the entire width thereof while being kept incontact therewith during the unidirectional motion, at least two printbuffers for feeding print data to control energization of the heatingelements of the thermal head, and a current on-time control circuit fordifferentially setting the on-time periods of a constant current to theheating elements of the thermal head in response to selection of theprint buffers under the predetermined condition that a basic color forgeneral print data is formed at a low temperature while a differentparticular color for specific print data is formed at a high temperaturein a printing operation on the recording paper by the heating elementsof the thermal head, wherein the current on-time is extended only whenthe print buffer for the different particular color has the specificprint data therein.

When the specific print data requiring the different particular color isstored in the print buffer, the current on-time for energizing theheating elements of the thermal head to execute high-temperatureprinting is prolonged to increase the print time, but in the basic-colorprint portion for which such specific print data is not needed andmerely the general print data alone is stored in the print buffer, thetime for energizing the heating elements of the thermal head isshortened to reduce the print time for that line, whereby the labelissuing efficiency can be enhanced and the label portion to beemphasized is printable without any difficulty.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary apparatus embodying thepresent invention;

FIG. 2 is a side view of a partial mechanism;

FIG. 3 is a plan view of a label; and

FIG. 4 is a timing chart.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter an exemplary embodiment of the present invention will bedescribed with reference to the accompanying drawings. First, asillustrated in FIG. 2, rectangular labels 1 as recording paper areattached at equal intervals onto an elongated mount paper 2 which iswound in the shape of a roll and is held on a label supply reel 3. Themount paper 2 moved forward via a platen 5 driven by a pulse motor 4 isbent through a label stripper plate 6 and then is wound, by way of aroller 7, around a takeup shaft 9 rotated by a takeup motor 8. A thermalhead 10 is located on the platen 5, and the label 1 separated by thelabel stripper plate 6 is forwarded to a label detector 11, which thendetects the presence or absence of the label 1 photoelectrically whiledetecting the passage timing of its leading edge.

FIG. 3 shows exemplary contents printed on the label 1. The peculiarinformation 12 preprinted on the label 1 includes production data,efficacy date, code, article number, unit price (=) per 100 g, quantity(g), shop name, partition line (printed in, e.g. blue); and price (=)(printed in, e.g. white on red ground). In addition thereto, specificinformation 17 including article name 13, date 14, bar code 15, data 16,"advertised article" and so forth is printed by the thermal head 10. The"advertised article" in the specific information 17 is the portion to beemphasized in this embodiment, and it is printed by the undermentionedmeans in a particular color which is different from the ordinary colorof the other printed portions. In further detail, the label 1 has, onits surface, two color forming layers with dichromatic temperaturecharacteristic, in which the upper layer is used for a basic color suchas black while the lower layer is used for a different particular colorsuch as red. In this example, when the current supplied to the heatingelements of the thermal head 10 is kept constant, the basic color(black) is formed on the lable 1 in a low temperature mode during whichthe current on-time is short, and the particular color (red) is formedin a high temperature mode during which the current on-time is long.

Now the electric circuit configuration will be described below withreference to FIG. 1, wherein a printer controller 20 is so incorporatedas to operate in response to a print command or a label detectionsignal. A scale 21 is connected to one input of each of two AND gates 22and 23, and the controller 20 is connected either directly or through aninverter 24 to another input of each of the AND gates 22 and 23. A firstprint buffer 27 and a second print buffer 28 are connected via charactergenerator converters 25 and 26 respectively to the outputs of the ANDgates 22 and 23. And the controller 20 is further connected via an Xaddress line, a Y address line and a clock line to both the printbuffers 27 and 28.

The second print buffer 28 is connected via an OR gate 29 to a shiftregister 30 in the thermal head 10. Meanwhile the first print buffer 27is connected to the input of an AND gate 31 together with a colorcontrol signal (C. CONT) obtained from the printer controller 20, andthe AND gate 31 is connected to the OR gate 29.

In the internal structure of the thermal head 10, the followingoperation is performed. First, data of the print buffers 27 and 28 areinputted bit by bit to the shift register 30 by the use of clock pulses(CLK), and the content of the shift register 30 is transferred bit bybit to a latch circuit 32, which is connected in parallel thereto, bythe use of a strobe signal (STB). To the latch circuit 32 are connectedAND gates 36 which control the current fed to the heating elements 35connected in common to a power supply 34 via a multiplicity of AND gates33. The AND gates 36 are opened by an enable signal (ENB).

A timer 37 serving as a current on-time control circuit is connected tothe printer controller 20. The timer 37 is started in response to asignal representative of a timer T1 and functions to determine a timeT2, during which the contents of both the first print buffer 27 and thesecond print buffer 28 are printed simultaneously, as will be describedlater. And a variable resistor 38 is connected to the timer 37 foradjusting the time T2.

Furthermore, a motor driver 39 coupled to the pulse motor 4 is connectedto the printer controller 20 so as to control the forward motion of thelabel 1.

In the structure mentioned above, a strobe signal STB and an enablesignal ENB are generated respectively at the rise of T1 and the rise ofT2. Assume now that the period T1 corresponds to the time required forprinting one line in a different particular color on the label 1, andthe pulse motor 4 is driven cyclically per T1 to feed the label 1 by oneline. It is defined here that "one-line printing" relates to one line ofunitary dots, not to one line of characters. The time T2 is determinedby the timer 36, and the period T1 is divided into the time T2 and thetime (T1-T2). It is supposed here that the output of the timer 36 isturned to a high level after the lapse of T2 from the start of T1.

The printing operation will be described below with the first printbuffer 27 referred to as A memory and the second print buffer 28 as Bmemory. Regarding the contents stored in the A and B memories, Xaddresses denote those for individual lines, and Y addresses denotethose in each line. Consequently the print contents of 0, 1, 2 . . . Y,Y are existent in each of the X addresses.

Referring now to the timing chart of FIG. 4, the operation starts from"N DATA A B MEMORY PRINT". In this portion, the heating elements 35begin to be energized according to the data already inputted to theshift register 30 in response to the STB signal and the ENB signal basedon T1. Since T2 is still at a low level in this stage, the C. CONTsignal also remains at a low level and therefore so serves as not tofeed the output of the A memory to the thermal head 10. Consequently, atthis moment, input data to the thermal head 10 is merely the content ofthe B memory, and the content actually printed is based on the datainputted immediately anterior to this stage.

After the lapse of the time T2, the content of the B memory inputted tothe shift register 30 is then applied to the latch circuit 32 toenergize the heating elements 35. Consequently the content of the Bmemory inputted previously is printed. Since T2 is at a high level, theC. CONT signal is also at a high level so that the data from both the Aand B memories are inputted to the shift register 30 in the thermal head10.

The label 1 fed by one line cyclically in the period T1 receives thecombined contents of the A and B memories and the content of the Bmemory alternately within the time length divided into a time (T1-T2)and a time T2, and is so processed as to print the received contentssequentially. Since the current on-time for energization includingmerely T2 becomes short to induce a low temperature, the content for thegeneral print data such as the article name 13 stored in the A memory isprinted in the basic color (black). Meanwhile, the specific information17 of "advertised article" in the content of the B memory is printed inthe different particular color (red) as the heating elements 35 areenergized for the time T1 which is long to induce a high temperature.Thus, the resultant color comes to be different from the otherinformation such as the article name 13 and so forth which are printedonly within the short energization timing T2, whereby the specificinformation 17 is rendered distinguishable with remarkable definition.

The operation described above is performed relative to the print lineincluding the specific information 17 which is to be printed in thedifferent particular color. In this embodiment, the print time isshortened for any print line of the bar code or the like where none ofthe different particular color is required, as shown in the secondone-line print portion in FIG. 4. It corresponds to the case where noneof the specific information 17 is stored in the related B memory, andthe data is stored merely in the A memory alone. Then, prior to lapse ofthe time T1, the current is supplied during the time T2 required forprinting the article name 13 and so forth and, posterior to the basiccolor (black) print time, a pulse of T1 is outputted for printing thenext line. Therefore, the required print time is shortened in the linewithout any of the specific information 17 to consequently reduce theentire label issuing time, hence enhancing the operational efficiencythereof. In other words, the current on-time corresponding to the printtime is extended in this embodiment only for the line requiring print inthe different particular color.

In a practical operation, the variable resistor 38 is adjusted properlyto change the time T2. Such adjustment is executed in accordance withthe paper quality of the label 1 and so forth.

Although in the above embodiment the "advertised article" is selectivelyprinted in a different particular color as the specific information 17,such particular-color printing may also be performed under the conditionthat individual items of various print groups (peculiar information 12)determined by preprinting on the label 1 are selectable with mutualcombination. In a modification of using a non-preprinted label 1, thepeculiar information 12 including a production date and so forth may beprinted in a different particular color by the thermal head 10 in thesame manner as the aforementioned, while the general data including anarticle name 13 and so forth may be printed in a basic color.Furthermore, when the characters such as "advertised article" to beemphasized are printed on a preprinted label 1, as already described inconnection with the foregoing embodiment, a sum (price) calcuated from(scaled weight)×(unit price) may be printed in the different particularcolor to become conspicuous. Especially when the unit price is low as inthis exemplary embodiment where the emphasized message includes"advertised article", it is preferred that the unit price be printed inthe different particular color (red). In such particular-color printingoperation, flags (e.g. red=1, black =0) for selecting a red pring modeor a black print mode may be previously stored in flag memories by akeyboard or flag setting commands with respect to the individual itemsof article name, auxiliary characters (e.g. advertised article), weightand price. And in the stage of preparing memory data to be stored in theprint buffers 27 and 28, black-forming data may be produced for theprint buffer 27 and red-forming data for the print buffer 28respectively in accordance with such selection flags.

What is claimed is:
 1. A thermal printer apparatus comprising:recordingpapers each having multi-color-forming temperature characteristic; athermal head containing a multiplicity of heating elements and capableof printing the recording paper over the entire width thereof whilebeing kept in contact therewith during its unidirectional motion; atleast two print buffers for feeding print data to control energizationof the heating elements of said thermal head; and a current on-timecontrol circuit for differentially setting the on-time periods of aconstant current to the heating elements of said thermal head inresponse to selection of said print buffers under the predeterminedcondition that a basic color for general print data is formed at a lowtemperature while a different particular color for specific print datais formed at a high temperature in a printing operation on the recordingpaper by the heating elements of said thermal head, wherein the currenton-time is extended only when said print buffer for the differentparticular color has the print data therein.
 2. The thermal printer asdefined in claim 1, wherein said recording paper has preprintedcharacters or the like such as a production date, and desired printcontents are selectively printable in the different particular colorwith respect to the individual items of various print groups determinedby such preprinting.
 3. The thermal printer as defined in claim 1,wherein said recording paper has none of preprinted characters or thelike such as a production date, and characters or the like correspondingto such preprinted ones are printed in the different particular colorformed by said thermal head.
 4. The thermal printer as defined in claim1, wherein, when the print content based on the specific print data is amessage such as "advertised article", "article for special sale" or thelike, the sum calculated from (scaled weight)×(unit price) or said unitprice is printed in the particular color which is the same as that ofsaid message.